That was the reason to deprecate the `interleaved` argument I believe. I have restored the deprecation warning in my last commit. Besides, the docstring should now warn the user with enough insistence that `interleaved` is to be used with high caution.

As for `slice_order`, there were two distinct reasons why it was suggested to deprecate it: 1) it does not conform to the SPM 'slice order' convention; 2) it's restrictive in that it cannot represent sequences with varying inter-slice acquisition time. The code now issues a warning if you use `slice_order` telling you to make sure that you are not using SPM-style slice order declaration. That's not a deprecation warning, but I think that should address concern 1. Moreover, `slice_times` is now implemented and you get a value error if you try to set both `slice_times` and `slice_order`, so 2 is also addressed. 

I have also come to think that `slice_order` is actually more handy than `slice_times` in many situations, provided that it's not confused with the SPM argument. Besides, recent discussions on the mailing list and elsewhere have encouraged me to keep the API as stable as possible.